A light-emitting diode (LED) is a kind of semiconductor device for converting electric energy into light. The LED has advantages of low consumption power, a semi-permanent lifespan, fast response speed, safety, and environment friendliness compared with an existing light source, such as a fluorescent lamp or an incandescent light. In particular, an LED light can perform various productions by controlling a flickering sequence, emitting color, and brightness of a plurality of arranged LEDs.
Active research is carried out on replacing an existing light source with an LED. The LED is the light source of a light, such as various indoor lamps, a liquid crystal display, an electric bulletin board, and a streetlamp, and the use of the LED tends to increase. In particular, the LED is used for a common light for an interior design, a stage light for producing a specific atmosphere, an advertising light, and a scene light.
A light device may be installed in the outer wall of a building, a park, a streetlamp, a bridge rail, or a theater as a scene light. The size and application system of the light device may be different depending on a use, object, or location to which the light device is applied. That is, light devices installed in the outer wall of a building are protruded from the outer wall of the building in a stripe form so that they perform a flickering function or display a single color or combined colors. Light devices installed in a park, a streetlamp, or a bridge rail are irregularly installed depending on the type of an object in such a way as to change flickering or colors. Furthermore, light devices installed in a theater are installed near or in the stage in a stripe form in such a way as to produce flickering or color so as to produce the magnificence of a theater. An outdoor light needs to be stably driven because it is difficult to maintain compared with an indoor light. Accordingly, various schemes for stably controlling an outdoor light are considered.
An LED light needs to be able to operate in standby mode in order to implement the LED light according to various purposes. Standby mode is a standby state in which although an LED is not turned on, it maintains a proper power level so that the LED can be driven anytime in response to a control signal from a power supply device for controlling the LED.
A conventional power supply device for an LED light has a single stage structure and a 2-stage structure. The 2-stage structure includes a separate circuit (i.e., a standby circuit) for implementing standby mode. The single stage structure has a simpler structure and smaller size than the 2-stage structure and does not include a standby circuit. The reason for this is that the single stage structure is not differentiated from the 2-stage structure if the standby circuit is inserted into the single stage structure, thereby increasing the size of the single stage structure. When an LED is turned on in the state in which a power supply device maintains a specific voltage without using a standby circuit, an overcurrent flows into the LED due to an instant voltage rise. As a result, there are problems in that a flash is generated from the LED and the lifespan of the LED is reduced due to the overcurrent.